1. Field of the Invention
The present invention relates to a lubricant supply device for supplying lubricant to a screw shaft of a rolling-member screw apparatus and to a rolling member screw apparatus using such a lubricant supply device.
2. Description of the Related Art
A rolling-member screw apparatus such as a ball screw has conventionally been known. The rolling-member screw apparatus comprises a screw shaft, a nut member and a plurality of balls. The screw shaft has a ball running groove formed spirally on the outer periphery of the screw shaft. The nut member is engaged with the screw shaft. The nut member has a ball circulation passage formed therein, which includes a loaded ball running groove formed spirally on the inner periphery of the nut member so as to correspond to the above-mentioned ball running groove. The balls are placed and received in the ball circulation passage. A relative rotation of the nut member to the screw shaft causes the balls to roll in the ball running groove so that the nut member can move linearly relative to the screw shaft.
With respect to a lubricant supply device for lubricating the ball running groove of such a rolling member screw apparatus, the present inventor made an invention of a lubricant supply device as shown in FIG. 10 (as disclosed in Japanese Patent Application No. H11-50922). The lubricant supply device comprises an application member 52 having tongue portions 51, 51 coming into contact with ball running grooves of a screw shaft to apply the lubricant on the ball running groove, a casing 54 for forming a lubricant storage member 53, from which the lubricant is supplied to the application member 52, and a joint member 55 for controlling an amount of lubricant supplied from the lubricant storage member 53 to the application member 52. An occlusion member 56, which absorbs the lubricant to store it, is fitted into the lubricant storage member 53.
When the tongue portions 51, 51 move, while coming into contact with the ball running grooves, the lubricant is supplied from the tongue portions 51, 51 into the ball running grooves. When an amount of the lubricant absorbed in the application member 52 is gradually decreased, the lubricant absorbed in the occlusion member 56 is supplied to the application member 52 through the joint member by capillary action. Accordingly, a prescribed amount of lubricant is always absorbed in the application member, thus making it possible to stably supply the lubricant from the tongue portions 51, 51 to the ball running grooves.
In the lubricant supply device disclosed in the above-mentioned Japanese Patent Application No. H11-50922, the single application member 52 has the tongue portions 51, 51, which are arranged in line in the axial direction of the screw shaft. The number of the tongue portions 51, 51 is equal to the number of the thread grooves of the screw shaft. The lubricant is supplied to the entire ball running grooves, irrespective of the number of the thread grooves of the screw shaft. Arrangement of the application member 52 below the lower portion of the lubricant storage member causes the lubricant to concentrate in the application member 52 by the function of gravity, thus gathering the lubricant in the single place to apply it onto the ball running grooves.
However, when the tongue portions 51, 51, the number of which is equal to the number of the thread grooves, are arranged in line on the single application member 52, the length of the application member 52 increases in proportion to the number of the thread grooves of the screw shaft, with the result that the length of the lubricant supply device in its longitudinal direction may become unnecessarily longer.
In addition, a user does not always mount the lubricant supply device on the ball screw so that the application member 52 of the lubricant supply device is placed on the lower side of the ball screw. When the application member 52 is not placed on the lower side of the ball screw, the lubricant received in the lubricant storage member 53 may not be supplied to the application member 52.
An object of the present invention is therefore to provide a lubricant supply device, which permits supply of substantially all the amount of lubricant received in the device to flow out and which has a decreased length of the device in the axial direction of the screw shaft, and a rolling member screw apparatus.
In order to attain the aforementioned object, a lubricant storage member is divided into a plurality of compartments arranged in the circumferential direction of the screw shaft. The number of the compartments is equal to or larger than the number of the thread grooves of the screw shaft. Application members are placed in correspondence to the compartments. Each of the application members has a tongue portion. More specifically, the lubricant supply device of the present invention, which is to be fitted to a nut member engaging with a screw shaft having at least two thread grooves through rolling members to supply lubricant to the screw shaft along with a relative rotational motion of the nut member to the screw shaft, comprises:
a plurality of application members for applying the lubricant on the screw shaft, each of said application members having a tongue portion, which comes into contact with rolling-member running surfaces of the screw shaft;
a casing for forming a lubricant storage member, from which the lubricant is supplied to said application members; and
a plurality of control members for controlling an amount of the lubricant supplied from said lubricant storage member to said application members,
wherein:
said lubricant storage member is formed into a cylindrical shape into which the screw shaft is loosely inserted, said lubricant storage member being divided into a plurality of compartments arranged in a circumferential direction of the lubricant storage member, the number of the compartments being equal to or larger than the number of said at least two thread grooves of the screw shaft;
said application members are placed in correspondence with the compartments; and
each of said application members has a tongue portion.
According to the present invention having the above-mentioned structure, the relative rotation of the screw shaft to the nut member causes the lubricant to be supplied from the tongue portions of the application members to the rolling member running surfaces of the screw shaft. The control members control an amount of lubricant supplied from the lubricant storage member to the application members. As a result, an amount of lubricant supplied from the lubricant storage member to the application members does not vary drastically in the course of time, thus leading to a constant supply of the lubricant in a prescribed amount from the application members to the screw shaft. It is therefore possible to apply the lubricant to the screw shaft in a minimum amount for a long period of time.
The relative rotation of the tongue portions to the screw shaft causes the tongue portions to move along the spiral rolling member running surfaces, while applying the lubricant onto the rolling member running surfaces of the screw shaft. The lubricant storage member is divided into a plurality of compartments arranged in the circumferential direction of the lubricant storage member. The number of the compartments is equal to or larger than the number of the thread grooves of the screw shaft. The application members are placed in correspondence to the compartments. Accordingly, the rolling member running surfaces can be lubricated entirely. In addition, almost all the amount of lubricant received in the lubricant supply device can be supplied to flow out, irrespective of the mounting posture of the lubricant supply device on an rolling member screw apparatus. Further, each of the application members has the single tongue portion formed thereon. It is therefore possible to prevent the application member from becoming longer in the axial direction of the screw shaft, thus providing the lubricant supply device having the decreased length in the axial direction of the screw shaft.
As the application member, there may be used material, which can smoothly apply the lubricant absorbed therein on the screw shaft, for example, oil absorbent material having a relatively low porosity, which is formed of fiber-entangled body such as felt, or of sintered resin.
With respect to the lubricant storage member, any structural component, which can store in its inside a large amount of lubricant supplied to the application member, may suffice. As the lubricant storage member, there may be used for example either a tank having in its inside a storage chamber for receiving the lubricant, or oil absorbent material including fiber-entangled body such as felt, sintered resin or sponge by which the lubricant is actually absorbed. The oil absorbent material preferably has a higher porosity than that of the oil absorbent material described above, which serves as the application member.
With respect to the control member, any structural component, which can control an amount of lubricant supplied from the lubricant storage member to the application member, may suffice. As the control device, there may be used, for example, oil absorbent material, which is formed of a fiber-entangled body, such as felt, or of sintered resin. The oil absorbent material for the control member preferably has a porosity, which is between the low porosity of the oil absorbent material for the application member and the high porosity of the oil absorbent material for the lubricant storage member. As the control device, there maybe used an oil supply adjusting plate, which can be obtained by forming supply holes, through which the lubricant can pass, on a thin plate separating the lubricant storage member and the application member from each other.
There may be adopted an inventive structure that said casing has a plurality of slits formed therein, said slits extending in a longitudinal direction of a central axis of the screw shaft so as to correspond to the compartments, respectively; and said application members are fitted into the slits, respectively. According to such an inventive structure, it is possible to prevent the application member from projecting from the lubricant storage member in the axial direction of the screw shaft, thus providing the lubricant supply device having its decreased length in the axial direction of the screw shaft.
There may be adopted an inventive structure that said casing has a cylindrical portion through which the compartments pass in the longitudinal direction of the central axis of the screw shaft. According to such an inventive structure, the compartments pass through the cylindrical portion in the axial direction of the screw shaft so as to avoid the complicated working required in the prior art. More specifically, the cylindrical portion can be manufactured by an extrusion molding method (or an injection molding method), thus providing the lubricant supply device at a low cost.
There may be adopted an inventive structure that said cylindrical portion has the slits passing through the cylindrical portion in the longitudinal direction of the central axis of the screw shaft. According to such an inventive structure, the more complicated working required in the prior art can be avoided. More specifically, the cylindrical portion having the compartments and the slits can be manufactured by an extrusion molding method (or an injection molding method), thus providing the lubricant supply device at a low cost.
There may be adopted an inventive structure that each of said application members and said control members comprises oil absorbent material, which can absorb the lubricant to store same; each of said application members is formed into a plate-shape, said each of the application members being placed in each of the slits so as not to come into contact with any one of the compartments; and each of said control members comprises a main body and an elongated portion, said main body being placed in the respective slit so as to come into contact with the respective application member, but so as not to come into contact with the respective compartment, and said elongated portion extending from the main body so as to come into contact with the respective compartment. According to such an inventive structure, the lubricant absorbed in the application member is applied onto the rolling member running surface of the screw shaft, while the lubricant stored in the lubricant storage member is supplied to the application member thorough the elongated portion and the main body of the control member. The optimum determination of the shapes of the elongated portion and the main body, a contact area of the elongated portion with the inside of the lubricant storage member and the contact area of the main body with the application member makes it possible to supply the lubricant from the lubricant storage member to the application member in a properly controlled manner.
There may be adopted an inventive structure that each of said compartments has an occlusion member fitted therein, said occlusion member absorbing the lubricant to store same; and porosity of the occlusion member, the control member and the application member are determined to be smaller in this order. According to such a structure, it is possible to preserve an amount of lubricant, which is required to be applied, in the application member and impart strength, which is sufficient to bear the contact slide with the rolling-member running surface, to the application member. Use of the oil absorbent material having a high porosity as the occlusion member makes it possible to ensure the sufficient amount of lubricant preserved therein. When the fiber-entangle body, which can cause capillary action, is used as material for forming the occlusion member, the control member and the application member, sucking force caused by the capillary action becomes larger in this order. Accordingly, no congestion of the lubricant in the passage therefor occurs, thus providing smooth supply of the lubricant.
A rolling member screw apparatus of the present invention comprises:
a screw shaft having at least two rolling member running surfaces formed spirally on an outer periphery thereof;
a nut member engaged with the screw shaft, said nut member having a rolling member circulation passage formed therein, said rolling member circulation passage including at least two loaded rolling member running surfaces formed spirally so as to correspond to said at least two rolling running surfaces;
a plurality of running members being placed and received in the rolling member circulation passage; and
a lubricant supply device for supplying lubricant to the screw shaft along with a relative rotational motion of the nut member to the screw shaft,
wherein:
said lubricant supply device comprises:
a plurality of application members for applying the lubricant on the screw shaft, each of said application members having a tongue portion, which comes into contact with a rolling-member running surface of the screw shaft;
a casing for forming a lubricant storage member, from which the lubricant is supplied to said application members; and
a plurality of control members for controlling an amount of the lubricant supplied from said lubricant storage member to said application members
said lubricant storage member is formed into a cylindrical shape into which the screw shaft is loosely inserted, said lubricant storage member being divided into a plurality of compartments arranged in a circumferential direction of the lubricant storage member, the number of the compartments being equal to or larger than the number of said at least two thread grooves of the screw shaft;
said application members are placed in correspondence to the compartments; and
each of said application members has the tongue portion.
The other lubricant supply device of the present invention, which is to be fitted to a nut member engaging with a screw shaft through rolling members to supply lubricant to the screw shaft along with a relative rotational motion of the nut member to the screw shaft, comprises:
a plurality of application members for applying the lubricant on the screw shaft, each of said application members having a tongue portion, which comes into contact with a rolling-member running surface of the screw shaft;
a casing for forming a lubricant storage member, from which the lubricant is supplied to said application members; and
a plurality of control members for controlling an amount of the lubricant supplied from said lubricant storage member to said application members,
wherein:
said lubricant storage member is formed into a cylindrical shape into which the screw shaft is loosely inserted, said lubricant storage member being divided into a plurality of compartments arranged in a circumferential direction of the lubricant storage member;
said casing has a cylindrical portion through which the compartments pass in the longitudinal direction of a central axis of the screw shaft.
According to the present invention having the above-mentioned structure, the lubricant storage member is divided into a plurality of compartments. It is therefore possible to supply almost all the amount of lubricant received in the lubricant supply device to flow out, irrespective of the mounting posture of the lubricant supply device on the rolling member screw apparatus. In addition, the casing has the cylindrical portion through which the compartments pass in the longitudinal direction of the central axis of the screw shaft. The complicated working as required in the prior art can be avoided. More specifically, the cylindrical portion can be manufactured by an extrusion molding method (or an injection molding method), thus providing the lubricant supply device at a low cost. The cylindrical portion may be formed integrally with the casing or the former may be formed independently from the latter.
In such a lubricant supply device of the present invention, there may be adopted an inventive structure that said casing has a plurality of slits formed therein, said slits extending in the longitudinal direction of the central axis of the screw shaft so as to correspond to the compartments, respectively; and said application members are placed in correspondence to the compartments and fitted into the slits, respectively; said cylindrical portion has the slits passing through the cylindrical portion in the longitudinal direction of the central axis of the screw shaft. According to such an inventive structure, the more complicated working required in the prior art can be avoided. More specifically, the cylindrical portion having the compartments and the slits can be manufactured by an extrusion molding method (or an injection molding method), thus providing the lubricant supply device at a low cost.